Bad healing is a little more subtle. If the tank is overgeared -- and a lot of them are nowadays -- you can get away with bad healing a lot of the time. I've had absolutely terrible healers get accolades from the DPS when, as a tank, I was scrambling to stay alive on almost every pull. Then, suddenly, they get a tank who has marginal gear (or even just normal gear for the instance) and they can't keep him up. Clearly it's not their
fault, they've run fifty heroics with Phatlootz McEpicpants from their guild, and never had a problem
. So it must be the tank's fault.